SiteMap Page 164

Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 Next

How can I measure the angle between two lines in ANSYS?

Use the *AFUN command to set the unit system - either RAD or DEG. Then, use the GET command ANGLEK (see APDL Guide Appendix B) to retrieve the angle:<br><br>e.g.,...

When a check box (tick-box) is enabled on a panel in CFX-Pre, sometimes the data which should be made available by enabling the check box does not appear.

This is a problem with the CFX-Pre user interface.

WORKAROUND:<br>Disabling and re-enabling the check box makes the relevant data appear again.<br><br>FIXED IN:<br>ANSYS CFX Release 12.0.

Importing a mesh from an ANSYS Meshing Database (*.cmdb) into CFX-Pre fails with the following message on Windows 32-bit machines:
"gtmDSDBReader.exe has encountered a problem and needs to close. We are sorry for the inconvenience."

One of the libraries used to import files of this type shows up a compiler optimisation problem on Windows 32-bit only.

WORKAROUND:<br>Set the options for CFX-Mesh to write GTM files only (Tools>Options>Meshing>CFX-Mesh options), and import the .gtm file into CFX-Pre instead of the .cmdb...

I have a group/component/selected set of nodes, and I want to find the average position. How can I do this?

This may be desirable in a number of situations; for example, to find the approximate centroid of a surface that was a named selection in Simulation.<br><br>You will have to *VGET an...

Class 3 Error

If the CFX Interpolator is used to interpolate the results from a multi-component flow onto a new definition file, then it is possible for the initial values created in the definition file to have the mass fractions for the components mixed up. For example, in a gaseous mixture, it may be that the mass fraction of oxygen is initialised to the mass fraction of nitrogen from the initial values file. This may not be obvious, particular for combustion cases where there may be a large number of components all with fairly small mass fractions.

A similar effect can be seen if the interpolator is used with results from a multiphase flow, where the initial values of volume fraction for the different fluids may be mixed up. This is usually obvious, because the initial conditions are so badly wrong (due to the fluids usually having such different volume fractions) that the simulation often crashes or has difficulty converging.

These problems cannot be seen by looking at the interpolated results in the definition file in CFX-Post, but can be seen by post-processing a backup or transient file that is written before the first timestep of the run.

The CFX Solver works with fixed internal names for the mass fractions and volume fractions of the components and fluids. For the restart to work correctly, the user names of the components or fluids (e.g. Water.Volume Fraction or N2.Mass Fraction) must be mapped to the same internal names in the restarted runas they were in the original run. For some interpolated runs (particularly those where the components or fluids have changed), this mapping is n

WORKAROUND:<br>For problems with volume fraction initial conditions being mixed up, the workaround is to swap the order of the fluids in the fluids list in the CFX Command Language (CCL)....

In CFX-Pre, for the LRR Reynolds stress model, the model constants can be modified under advanced control. What do the constants
LRR IP RS COEFFICIENTS/ C1 Coefficient and
refer to? There is no obvious match between these names and the constant names for the pressure strain correlation given in the documentation.

<br>The pressure strain correlation given in the documentation can be reformulated differently. For the LRR-IP Reynolds stress model, this leads to a simplification, with only two terms...

How can I calculate the positive and negative mass flows through an opening boundary in CFX-Post?

There are two ways you can do this. Note that both of these methods will give slightly different answers than the mass flows seen by the CFX-Solver. This is because the solver calculates mass...

Class 3 Error

If a vector magnitude variable, such as Velocity.trnmax, is used in CFX-Post, then behaviour unexpected to the user may result. This is because CFX-Post calculates Velocity.trnmax as the amplitude of the vector formed from the components Velocity u.trnmax, Velocity v.trnmax and Velocity w.trnmax and not the transient maximum of the amplitude of the Velocity vector at times throughout the simulation.

This is caused by a difficulty with the definition of these comple

WORKAROUND:<br>The user can work around this difficulty by creating an Additional Variable equal to the amplitude of the vector variable required, and calculate transient statistics for...

Class 3 Error

Some cases which use a mass-flow specified outlet with the "Shift Pressure" option for the "Mass Flow Update" setting result in a mass flow which does not match what the user has set. This only affects cases which are run in parallel and where artificial walls are built at the outlet (to prevent fluid from flowing into the domain).

When the "Shift Pressure" option is used, the algorithm which calculates the appropriate pressure shift needs to iterate to determine the pressure shift when artificial walls are present. In parallel, a coding error means that the iteration never happens and the pressure shift is not updated properly

WORKAROUND:<br>No workaround is currently available. The user may be able to avoid the problem by modifying the initial conditions and/or boundary condition settings so that artificial walls...

In some chemistry calculations, it is possible to use the 'Equilibrium' reaction option despite it being physically invalid. The CFX-Solver treatment for this changed in CFX-11.0, viz.:

1) In CFX-10.0 and earlier versions of CFX-5, and also in CFX-4, the recipe for 'Equilibrium' is applied regardless of it being physical invalid. However, this has significant drawbacks:
- The backward rate has wrong physical dimensions! The dimension are wrong by factor [m^3n mol^-n] whenre 'n' is a number of order O(1).
- Forward and backward rates to not balance in chemical equilibrium, i.e. the mixture composition does not converge towards the chemical/thermodynamic equilibrium, but will approach some other composition.

2) Since CFX-11.0 a correction to the 'Equilibrium' option is applied such that the backward rate has the correct dimensions and that the forward/backward rates balance when in equilibrium. The drawbacks in this approach are:
- The stiff chemistry solver may not converge in many cases, and there is no obvious way to fix this.
- The reaction mechanisms may have been developed assuming approach 1), because this is what everybody else is doing.

Unfortunately, users may expect treatment 1) to operate, despite its drawbacks.

This is due to an improvement to the software conflicting with user expectation.

WORKAROUND:<br>No workaround is currently available.<br><br>FIXED IN:<br>ANSYS CFX Release 12.0. In CFX-12.0, users will be able to use an expert parameter to choose from...

If a case contains automatically generated interfaces, and those interfaces were generated as a result of 'contact' information in the original cmdb file, it is possible that a subsequent import of a def file created from this set-up would lose this connection and the interface would then be missing from the set-up.

This is due to not all connection data of this type being written into the def file.

WORKAROUND:<br>Use the cfx file, which has topological information correctly stored.<br><br>FIXED IN:<br>ANSYS CFX Release 12.0. Note that this fix only corrects the...

Class 3 Error

In transient multiphase mass flow discretization, the lagged transient term in coupled Rhie-Chow is wrong by a factor of density. This affects all transient inhomogeneous flows, with the error greater for smaller timesteps.

There is a coding error in the coding

WORKAROUND:<br>No workaround is currently available.<br><br>FIXED IN:<br>ANSYS CFX Release 12.0. A custom executable for ANSYS CFX 11.0 SP1 is available on request.

I am trying to conduct an analysis on a two-part assembly; however, when I imported the geometry into ANSYS, it only imported the simpler part of the geometry and not the complex part. I tried to import geometry through DesignModeler but had the same problem. What is the problem, and how can I fix it?

I suspect that your complex part may have both solid and surface bodies in it, for which the default behaviour is to not import these bodies.<br><br>You could try setting the...

Class 3 Error

If data imported on a User Surface or Polyline is evaluated using an expression in a table, the function calculator or using macros, then the result may be incorrect. For example, if User Surface 1 is created and imports the data "p on User Surface 1", then evaluating "minVal(p on User Surface 1)@User Surface 1" may give an incorrect result. Note that plotting "p on User Surface 1" will still show the correct results.

If the data is not specified in SI units, then the units conversion is not handled correctly. Usually this wil

WORKAROUND:<br>Use SI units for the data in a Polyline or User Surface file.<br><br>FIXED IN:<br>ANSYS CFX Release 12.0.

When I do a modal analysis, the mode shape only shows up graphically on the screen if /ESHAPE is turned off for the beams. If /ESHAPE is turned on, the mode shape does not show up on the screen.

Please try issuing MXPAND,,,,YES. This needs to be set for ANSYS to save the element results for every mode.

By creating a surface out of existing curves the programm crashes with the message: segmentation error.
Known Problem in ICEM CFD 11.0.1, fixed in version 12.

Explanation: The model was examined with build diagnostic topology. Later some new lines were created in this modell which are unassigned for ICEM CFD. When trying to build a surface from these unassigned curves the build topology process crashed.

Deactivate the option create surface topology in Settings > Geometry options. It prevents ICEM CFD from checking automatically<br> changes in the topology.

I have a model with about 1 million DOF and I solve for about 1000 modes using QRdamp. I found that the analysis was too slow and took too much scratch space. Is this a system issue or a solver issue?

The QRdamp solver was designed to solve for a small number of modes (e.g., about 50), and is not optimized for speed when a large number of modes are requested.<br><br>For this...

How do I apply a boundary condition to an external boundary of a solid domain to account for heat loss through thermal radiation, without modeling the external fluid field? I can account for convection heat losses by setting a Heat Transfer Coefficient and an Outside Temperature, but there's no option for radiation unless the solid domain is connected to a fluid domain.

<br>You can account for radiative heat losses by modifying the Heat Transfer Coefficient at the boundary. Heat loss through convection only is given by:<br><br>q = h ( Tout...

Is there any theoretical documentation for DOE method used in DesignXplorer?

Yes, please see the attachment.

####### WORK NOTES COPIED FROM INCIDENT 805569 ########
Q : What does the projection limit mean??? What does a value of 1.3 mean???

The projection limit keeps the mesh from resolving small tolerance differences between the curves adjoining and geometry surfaces.<br>Also allows the user to bypass projection where surfaces...

Is there an animated demo available illustrating nonlinear material curve fitting procedures in ANSYS Classic?

On the ANSYS Website, go to the demo room and browse by products, select ANSYS Mechanical, refer to the last demo in the list.<br><br><a target=_blank...

Are there any examples of how to set up a layered shell in Workbench Simulation?

Attached is a simple Simulation database file that has three model branches. The first branch has a single-layered shell, the second two single-layered shells bonded with contact, and the third...

Why does ANSYS not allow the nonlinear combination of implicit creep and MKIN?

This is a current code limitation. The coding is not trivial for the MKIN plasticity because of the changing tangent slope as you progress through the loading. Enhancement request 76770 has been...

There are APDL commands in the ANSYS manual that can be used to bring up a window as a message box or an input box. How can I do something similar using APDL from within Workbench?

There are two approaches:<br><br>(1) In a command object in Simulation, add the following line:<br><br>/sys,msg %username% "This is my...

I need to vary Young's modulus with spatial variables (x and y) linear isotropic material. How can I do this?

Please find the attached example, in which Young's moduli are defined as an array. An area is then created and meshed. Nodes are selected based on their locations, and Young's...